A study on the hepatic response to heat stress in Gymnocypris eckloni through an approach combining metabolomic and transcriptomic profiling

Gymnocypris eckloni, an economically important cold-water fish widely cultivated in southwest China, is at increased risk of prolonged exposure to heat stress owing to persistent high temperatures in summer, extreme climate changes, and expansion of factory farming. In this study, G. eckloni was subjected to both chronic and acute heat stress, with subsequent analysis focusing on changes in the pathological and physiological characteristics and transcriptomic and metabolic responses of the liver to high temperature. The results revealed heat stress-induced damage to liver tissues, lipid accumulation and mitochondrial abnormalities in hepatocytes, and an increased number of apoptotic cells, with the damage being more severe under acute heat stress conditions. Assessment of biochemical indices showed that the antioxidant enzyme catalase (CAT) was activated in response to oxidative stress and energy demands increased following heat stress. Transcriptomic analysis showed significant enrichment in the protein processing in the endoplasmic reticulum pathway, along with upregulation of key genes associated with protein degradation (hsp40, hsp70, hsp90, ero1l, and pdia4) and activation of the unfolded protein response (UPR), which effectively reduces or clears the accumulation of misfolded proteins to combat stress. Most identified differential metabolites were associated with amino acid and lipid metabolism under heat stress. Notably, integrated transcriptomic and metabolomic analysis suggested that tryptophan metabolism played an important role in the adaptation of G. eckloni to chronic heat stress. These findings improve the understanding of the mechanisms through which G. eckloni adapts to high temperatures, providing a valuable foundation and novel avenues for developing strategies to alleviate the effects of heat stress and improve the outcomes of aquaculture.